The present invention relates to a data base access request processing system in a distributed data base system, and in particular, to an access request processing system suitable to perform processing between a system on a client side and a system on a server side in a concurrent fashion and to minimize the number of communications to be performed for the processing in the distributed data base system.
In a conventional access request processing system for controlling an access to a distributed data base, as disclosed in the JP-A-56-94433, in order to reduce the communication overhead, an update request and update data are retained in a stack queue of the system on the client side such that when a reference request is issued, the update request and the update data are sent to the system on the server side. Consequently, considerations have not been given to a possibility of concurrent processing in the systems on the client side and the server side.
In the prior art described above, when the system on the client side requesting a data base access sends a data base access request to the system on the server side effecting the data base service, the system on the server side returns a response to the system on the client side only after the entire data base processing associated with the request is completed.
In this method, however, in the period of time when the system on the server side is achieving the data base processing, the system on the client side is in a state waiting for a response from the system on the server side. This causes a significant problem in that the execution time is increased in the system on the client side.
The present invention address the situation above in order to solve the problems of the distributed data base access processing system of the prior art. Incidentally, among the data base access requests of the system on the client side, those related to a reference operation are processed such that an entity of data is transferred from a data base located in the system on the server side. Consequently, the data base reference processing of the system on the server side cannot be continued on the client side until the data entity transfer is completed because of the absence of the entity of the data in the system on the client side. For requests concerning an update operation, however, even after the entity of the updated data of the system on the client side is transferred to the system on the server side, the data entity exists in a buffer of the system on the client side. Hence, the processing on the client system can be effected without necessitating a wait state to wait for a transfer completion report from the system on the server side in an asynchronous fashion with respect to the processing in the system on the server side. Paying attention to this fact, in accordance with the present invention there is provided a distributed data access request processing system which enables a concurrent processing to be achieved in the systems on the client and server sides and which is capable of minimizing the executing time in the system on the client side.